A significant cause of infertility is disruption of normal embryo implantation. Molecular influences on this process have not been completely identified. A possible influence on implantation and female fertility might be via a bioactive lysophospholipid called lysophosphatidic acid (LPA). LPA activates G protein-coupled receptors (GPCRs) to exert its signaling effects. We have used homologous recombination to the third LPA receptor (called LPA3), and in preliminary studies, have observed reduced fertility attributed to delayed implantation and aberrant embryo spacing in mice lacking this receptor. Interestingly, the phenotype of LPA3- deficient female mice is remarkably similar to that seen in pregnant rats treated with indomethacin or mice deficient for cytosolic phospholipase A2a (cPLA2a), suggesting,a link between prostaglandins (PGs) and LPA signaling. In this proposal we will test the hypothesis that multiple lysophosphatidic acid (LPA) receptors influence embryo implantation. Three aims will be pursued. Aim 1 will determine roles for LPA signaling during implantation by examining LPA/LPA biosynthetic enzymes, and receptors expressed during implantation, with a focus on LPA3and LPA4. Aim 2 will determine the role of prostaglandins (PGs) on LPA signaling in implantation. Aim 3 will determine the mechanisms through which LPAs signaling interacts with PGs. As a pharmaceutically tractable molecule, lysophospholipid receptors could represent a new target for the therapeutic treatment of infertility. Work from this proposal will lay the groundwork towards realizing this possible therapeutic potential.